Organ transplantation is one of the great success stories of modern medicine. However, the supply of suitable organs lags far behind the need and many patients die while waitlisted for organs. Current practice involves "donor preconditioning" to stabilize organs and tissues for transplant in attempts to increase the supply of donor organs acceptable for transplantation. A key goal of preconditioning is to reduce the damage inflicted by ischemia-reperfusion injury (IRI) that occurs when the ischemic/ hypoxic organ is connected to the recipient's circulation. This storm of reactive oxygen species, inflammatory mediators and prothombotic factors threatens to kill the new organ and wreaks havoc upon the recipient as well. Current work indicates that enhancing the low levels of nitric oxide (NO) produced by eNOS and nNOS can dramatically improve IRI and transplant outcomes. The founders of Vasculox, Inc have discovered a receptor, CD47, that continually opposes the action of beneficial NO in all vascular cells. Knocking out CD47 in mice or blocking CD47 with a monoclonal antibody (mAb) results in enhanced tissue perfusion in a number of surgical ischemia models and protection from IRI in both liver and hindlimb models. In this phase one proposal, we seek to perform proof of concept studies in a well-characterized rat model of liver transplantation, testing the efficacy of anti-CD47 mAb treatment of the donor liver to protect it from IRI. Here we will compare the best case scenario in which anti-CD47 mAb is administered to the donor rat and maintained throughout liver harvest, cold storage and reperfusion, with the worst case of no CD47 blockade. In our protocol, the heart-beating donor rat will be treated with anti-CD47 mAb, the liver harvested and flushed with anti-CD47 mAb, subjected to cold storage ischemia and then rewarmed in the presence of mAb under controlled conditions of machine reperfusion. After a fixed interval of reperfusion, levels of released soluble liver enzymes and inflammatory mediators will be assayed, tissue taken for assays of ATP and cyclic nucleotides and the liver fixed for quantitative cytologic analysis and histochemical staining for the distribution of the anti-CD47 mAb and apoptosis (TUNEL and cleaved caspase). A simplified nonheart-beating donor model will also be performed when a period of warm ischemia is interposed between mAb administration and organ harvest. The data obtained in this phase I project will establish proof of concept for anti-CD47 mAb therapy in this liver transplant model. Phase II will address the "real world" situation of transplantation of treated or control livers into living recipients that can then be treated (or not) with the anti-CD47 mAb. While we have chosen to focus here on the liver model, we anticipate that anti-CD47 therapy will be of benefit in the transplantation of other organs (heart, kidney, lung, etc) as well as in surgeries involving organ resection for trauma and cancer and, potentially, in myocardial infarction and stroke. PUBLIC HEALTH RELEVANCE: The founders of Vasculox Inc, have discovered a regulatory receptor, CD47, that inhibits nitric oxide signaling in all vascular tissues. Nitric oxide provides many beneficial effects in the vascular system, including limiting ischemia-reperfusion injury. Therefore blocking CD47 and removing nitric oxide inhibition improves ischemia-reperfusion injury and holds promise as a means to improve the condition of organs destined for transplant and to control the damage to the recipient caused by ischemia reperfusion injury. Vasculox is developing a monoclonal antibody that targets CD47 and in this project aims to test the efficacy of such an antibody in a rat model of organ harvest, transport and reperfusion.